NASCAR racecars are primarily built in a two-step process. The first step is construction of the chassis, which consists of a central roll cage, a front clip, and a rear clip. A typical chassis is illustrated in FIG. 1. The second step is attachment of an outer body shell to the chassis. The chassis is constructed of round and square rails with varying thicknesses and dimensions. The size and shape of most of the rails (also called “tubes”) used in the chassis is strictly mandated by the NASCAR sanctioning organization.
Construction of the chassis is itself a four-step process. First, the trailing arm crossmember (TACM) is constructed and is used to set the reference frame of the car. In other words, application of all of the subsequent parts in the chassis is based on the dimensions and position of the TACM. The next step is building the front and rear clips that attach to the main longitudinal frame rails. The front and rear clips are constructed according to suspension “hard points” requirements of each team. The frame rails are also built to suit the heights required for different speedways. Different corners of a vehicle chassis can have different resting heights depending on the requirements of a given speedway. In the third step, the central roll cage is constructed. The roll cage consists entirely of round tubes of varying sizes and thicknesses. Lastly, the firewalls, floor pans, and roll cage are attached to the frame rails and the front and rear clips to complete the chassis. Traditional welding techniques are used according to NASCAR specifications during chassis construction.
Due to varying frame rail height requirements and because all of the subsequent parts in the chassis are dependent on the dimensions of the TACM, the construction of the TACM is an important step in the chassis construction process. The TACM consists of, as illustrated in FIGS. 2A-2D, a driveshaft hoop, trailing arm (also called “truck arm”) mounts, and the crossmember portions that attach to the frame rails. Support gussets may be use to strengthen the crossmember. Because the shape of the TACM changes for different frame rail heights and may require offset heights of crossmember portions, chassis construction must be changed for each configuration of the chassis. The height of the crossmember can be described as its distance from the ground when in use. This can also be referred to as vertical height of the crossmember. Also, the crossmember is cut and trimmed separately for each configuration. This can increase the cost, timing, and consistency of the TACM.
A trailing arm suspension is a vehicle suspension that includes one or more arms that are connected between the axle and the chassis (here, the crossmember of the chassis). The arms generally extend from the rear axle to a location on the chassis (the crossmember) that is forward thereof. Two arms are usually used.